1. Field of the Invention
The invention relates to an installation designed for remotely carrying out the taking of fluid samples, such as radioactive liquids within a confined area positioned below a biological protection slab.
2. Description of the Related Art
Several installations of this type can be placed in an irradiated nuclear fuel processing plant in order to carry out in an automated, remote manner the taking of samples of active solutions in different parts of the plant. They make it possible to introduce in a controlled manner fluid samples into containers known as pots, which are made from flexible plastic materials and which have been previously placed under a vacuum, prior to analyzing the said samples in the laboratory.
In order to ensure an optimum biological protection of personnel against .alpha. particles and .gamma. rays, without having to give to the equipment used an excessive weight and volume, FR-A-2 515 350 proposes carrying out the sampling operations directly within a vessel positioned below the biological protection slab. For this purpose the pots pass through the slab before being engaged on needles located in the bottom of the vessel and towards which are moved various fluids to be subject to the sampling operations. To this end, each of the needles passes, below the bottom of the slab, into a container supplied with fluid by a circuit, such as that described in FR-A-2 516 242.
In such an installation, the main problem is the transfer of the pots through the slab, as well as the actual sampling operation, which must be carried out blind and in an automated manner.
The solution to these problems described in FR-A-2 515 350 is completely mechanical. Thus, when introduced into the installation by a pneumatic transfer system, the pot is moved by a horizontal piston up to the upper end of a well in which its descent is controlled by the rotation of a vertical endless screw traversing the slab. In the bottom of the well, the pot is taken up by a vertically axed rotary barrel, where a rotation thereof has the effect of bringing the pot below a gripping tool traversing the said slab. This gripping tool controls the descent of the pot and ensures the sampling by engaging the pot on the needle. In order to have access to several needles arranged along one or more circular arcs in the vessel bottom, said assembly is installed on a rotary plug belonging to the slab and whose axis coincides with that of said circular arcs.
Such a mechanism is relatively complex and suffers from unacceptable risks with regards to the jamming of the pots, particularly when the latter are moved by the piston and during their descent into the well controlled by the endless screw. It is clear that the jamming of a pot when traversing the slab would involve a particularly difficult and dangerous intervention on behalf of the personnel.
Moreover, the installation described in the aforementioned document involves, when sampling has taken place, a discharge of the pots through the bottom of the vessel, which is compatible only with difficulty with the conventional arrangement of the laboratory for analyzing the samples taken outside the confined area. If it was considered that the filled pots should be evacuated by again passing them through the slab with the aid of the aforementioned mechanism, this would give rise to the use of various not described means, because the piston only permits pot transfer in one direction.